Idling system for two-cycle engines



Aug. 21, 1956 Filed Jan. 21, 1954 M. E. JONES IDLING SYSTEM FORTWO-CYCLE ENGINES 2 Sheets-Sheet l H B /7 ,5 so 7 I8 l I 1 8/ k l l l Fl G. 2

INVENTOR.

MALDWYN E. JONES ay z/ w ATTORNEY Aug. 21, 1956 M. E. JONES 2,7 7

IDLING SYSTEM FOR TWO-CYCLE; ENGINES Filed Jan. 21, 1954 2 Sheets-Sheet2 INVENTOR. MALDWYN E. JONES gm w ama ATTORNEY States atent Free IDLINGSYSTEM FOR TWO-CYCLE ENGINES Maldwyn E. Jones, Ferguson, M0., assignorto ACF Industries, Incorporated, New York, N. Y., a corporation of NewJersey Application January 21, 1954, Serial No. 405,336

2 Claims. (Cl. 261-41) This invention relates to fuel feeding and fuelmixture distribution systems for internal combustion engines. Morespecifically, the invention resides in a charge-forming devicecomprising a novel combination of a carburetor with a plurality ofintake manifolds for proper fuel distribution in different ranges ofengine speed. The novelty resides in the manner of interconnection ofthe elements of the combination, one with the other, wherein part or allof the fuel mixture can be supplied by the carburetor to the engineintake ports through one manifold in one range of throttle openings andengine speeds, or part or all of the fuel mixture can be supplied by thecarburetor to the engine intake ports through another manifold in otherranges of throttle openings and engine speeds.

One of the disadvantages of the usual carburetor manifold combinationsis unequal distribution between the cylinders of a multi-cylinderengine. This disadvantage may arise .at different engine speeds fordifferent engine manifold combinations, and has been found, as a matterof practical design, to be unavoidable in at least some degree in anydesign. By way of example, if it is possible to obtain gooddistributionat idle and in the full throttle range of the carburetor, then it oftenoccurs that the distribution in the part-throttle ranges of thecarburetor is wholly unsatisfactory. The engine operation may be eX-ceedingly rough at speeds above idling, due to the fact that only someof the cylinders will receive an ignitab'le mixture.

On the other hand, by way of example, if it is possible to obtain gooddistribution Within the part-throttle and full-thrott1e ranges of thecarburetor, then distribution at idle is wholly unsatisfactory. Whereeither of these conditions prevails, it often occurs that the cause maybe traced to the collection of fuel somewhere in the manifold in apuddle.

Under conditions such as those above explained, the present inventionmay be utilized to obtain satisfactory distribution throughout theentire range, including all throttle openings and all engine speeds. Inthis invention, the carburetor is mounted on a primary fuel mixturedistributing manifold connected to the engine intake ports. The usualidle fuelnozzle adjacent the edge of the carburetor throttle valve iseliminated. Instead, a plurality of nozzles are located adjacent a valveintake port to the engine within the primary manifold, and are suitablyconnected by a secondary fuel mixture manifold with the idling system ofports and passages in the carburetor.

During engine idling, the proper amount of fuel is metered by thecarburetor idling nozzle system, and is delivered to the individualcylinders adjacent each cylinder intake by the secondary manifold. Thiseliminates the effect on distribution during idling caused by pulsationsWithin the manifold, and the effect of unbalance of flow therein createdby the pulsations or by unevenly timed intake cycles, if such be thecase.

The carburetor used in this invention contains within the main mixtureconduit a suitable high-speed fuel nozthrottle range to supply theprimary manifold with a mixture sufficient to supplement that suppliedby the idle system of the carburetor through the secondary manifold.This supplies the demand at increased engine power outputs foradditional air and gasoline.

At the part-throttle range, distribution is aided by the supplementaryfuel and air delivered by the secondary manifold because throttledeflections cannot affect distribution by the secondary manifold fuelnozzle. Furthermore, since, within the part-throttle range at least, asmaller amount of liquid fuel is delivered to the engine by the primarymanifold, puddling of the fuel within the primary manifold iseliminated. This can be readily understood when it is realized that themixture carried in the primary manifold is much more lean in fuelcontent than would ordinarily be the case. Where, in a manifold, themixture contains a smaller weight of fuel, the weight of air suppliedbecomes larger in proportion to the weight of fuel and more effective asa fuel carrier because the saturation effect is reduced, causing lessaccumulation of fuel along the walls of the primary manifold.

In the full thi-ottle range of operation of the engine, operation of thesecondary manifold is not required, because engine speeds create an airvelocity in the manifold ordinarily sufficient to give gooddistribution. However, if desired, the fuel system in the carburetor canbe so adjusted that the secondary manifold will be supplied with fuelmixture throughout the entire range of throttle openings and enginespeeds.

In order to illustrate the invention, reference is made to theaccompanying drawings, in which:

Fig. 1 is a top plan view of a carburetor and manifolds according to thepresent invention.

Fig. 2 is a side elevational view in section of the carburetor andmanifolds shown in Fig. 1.

Fig. 3 is a front elevational view on a reduced scale illustrating themixture passages within the manifold shown in Figs. 1 and 2.

:Fig. 4 is a modification of the invention illustrated in Figs. 1 and 2showing a different form for the secondary manifold.

Referring now to the drawings in detail, the chargeforming deviceillustrated is specifically designed for a tandem, two-cylinder,two-cycle engine such as commonly used on outboard marine engines, chainsaws, mowers, and gasoline power driven, portable implements. Bu!t itshould be understood that the invention is equally applicable to enginesof a larger size wherein the manifold on the engine may be of entirelydifferent configuration, and to four-cycle engines as well.

In Fig. l the carburetor body casting 2 is formed with a mixture conduit3 containing a venturi 4. Posterior of the venturi 4 is a throttle valve5 suitably mounted on a throttle shaft 6 rotatable in bearings 7 and 8within the main carburetor body casting 2. The throttle valve 5 isdesigned to be closed in sealing relation to the mixture conduit 3 and,when closed, suitable air adjustment for engine idling conditions issupplied through a pair of apertures 10 and 11, which can be suitablycalibrated for the urpose. Fixed to the throttle shaft 6 is a throttlearm 13 which mounts a pin 14 for cooperation with the usual cam actuatedby the manual operated speed controller for the outboard engine. Torsionspring 15 surrounds the throttle shaft 6 and has one end hooked at 17for abutting engagement with throttle arm 13. The opposite end of thesprin E5 is engaged by the fixed abutment 18 in the carburetor bodycasting 2. Spring 15 tends to maintain the throttle 5 closed in themixture conduit 3.

Anterior of the venturi 4 and mounted within the mixture conduit is achoke valve 20 suitably mounted upon a rotatable choke shaft 21. An arm22 is fixed to the choke shaft 21 to provide a manual control.

The carburetorbody casting 2 is formed with a dependent, intcgralbosslocated opposite the throat of the venturi 4. Threads 26 within the boss25 receive threaded nipple 27 with an integral flange which abuts theperiphery of an aperture within the fuelbowl 28 and secures the bowl tothe carburetor body casting 2,- as illustrated in Fig. 2. Suitablegaskets are provided between the aperture of the bowl and the end of theboss 25, as well as the upper rim of the bowl 28 and the body casting2,to prevent the leakage of fuel from within the fuel'bowl 28.Surrounding the boss 25 and within the fuel'bowl28 is a float 36 foroperating a needle valve (not shown) in the fuel supply inlet to thefuel bowl 28.

A fuel passage 32 communicates between the fuel bowl 28 and the interiorof the hollow boss 25. This inlet is located'above the end of the nipple27, which is suitably threaded interiorly to receive a needle valve 35.A suitable packing gland 36 is provided for the needle valve whichextends upwardly within the boss 25 into an orifice 37' of a main fuelnozzle 40, which is exposed to the flow of'air in the throat of theventuri 4. The fuel nozzle 40 is suitably secured by its threaded end 41within the boss25.

The low speed nozzle system is supplied with fuel by idle tube 45press-fitted in the wall of the body casting 2. A plug 46 is threaded ina boss in the carburetor main body casting 2 forming a chamber incommunication with idle tube 45. The idle tube 45 projects downwardlywithin the main fuel nozzle 40 to a point adjacent the main orifice 37below the fuel level.

Within the main carburetor body casting 2 is a passage 50 shown in Fig.2 extending from an orifice 51, anterior of throttle valve 5, to thechamber above the idle tube 45. A passage threaded as at 56 receives anidle adjustment screw 57. Passage 55 is in communication with the idletube 45, and the idle screw 57 cooperates with a metering orifice 59 forcontrolling the flow of the mixture of fuel and air from idle tube 45and orifice 51 to outlets 60, one of which is shown in Fig. 2.

Turning now to Figs. 1 and 3, the carburetor main body casting 2 isflanged at 62 and secured to a manifold 65 by a pair of cap screws 66and 67. The mixture conduit 3 communicates with a U-shaped passage 69within the manifold '65, and is located in one of the legs of theU-shaped passage as illustrated in Fig. 3. Adjacent the ends 70 and 71of the U-shaped passage are engine intake valves 73 and 74,respectively. As shown in Fig. 2, these are triple valves, in thisinstance, provided with individual operating flexible reeds 75 and 76.The primary manifold is suitably apertured about its periphery toreceive bolts for securing the manifold to the engine. it also has apairof openings illustrated as 79 and 80 in Fig. 3, through which projectfuel nozzles 81 and 82 connected with branches of a secondary manifold84 and 85, which, in turn, are connected to the outlets 60 of the lowspeed or idling system of the carburetor.

An outboard engine of the type under consideration here is provided withan engine speed controller as mentioned above,-which is, in turn,connected with both the spark advance mechanism of the magneto and witha cam which cooperates with the follower pin 14 of the carburetor.Operation of the controller in one direction advances the spark from aretarded position, and the cam co-operating with the follower 14 is sodesigned that during this movement to advance the spark, the throttlevalve 5 remains stationary in a closed position. After the controllerhasadvanced the spark to speed the engine from a' slow idle to a fast idlespeed, the cam operated by 'the controller progressively opens thethrottle by coaction with the follower 14.

With the spark fully retarded by the controller, throttle 5 will beclosed, and main fuel nozzle 40 inoperative. The ports 10 and 11 in thethrottle allow the passage of some air through the mixture conduit 3into the primary manifold passage 69, and from thence to the intakevalves of the engine. While the throttle is closed, however,.and thefuel nozzle 40 is inoperative, most of the primary manifold will be dry,since no fuel will be supplied thereto.

The fuel supplied to the engine in the idle range of speeds with thethrottle valve 5 closed is delivered exclusively by the secondarymanifold. The fuel in the secondary manifold is in the form of a mixtureof air and fuel, however, due to the fact that suction on the fuelnozzles 81 and 82 will not only siphon fuel through the idle tube 45,but also air from the port 51 which, with the throttle closed, forms anatmospheric bleed. The port 51 has been shown adjacent the throttlevalve 5 so as to be swept by air passing around the throttle valve 5during its opening movement, but this is not absolutely necessary, andthe location of the port 51'at this point is purely optional. Air fromthe port 51 will mix with fuel from the idle tube 45 and pass throughthe metering orifice 59 under control of the needle valve 57. Thismixture will then enter the secondary manifold through the ports 60 andflow directly to a point adjacent the intake valve of the engine throughthe tubes 84 and 85 and the fuel nozzles 81 and 82.

The location of the fuel nozzles 81 and 82 provides for evendistribution of the air and fuel mixture passing through the secondarymanifold, while the air passing through the metered ports 10 and 11furnishes the additional air necessary to maintain a proper combustiblemixture and at the same time prevent the accumulation of fuel within theprimary manifold passages 69.

As the controller for the engine is operated to advance the spark,engine speed will increase from 400 or so R. P. M. to approximately1,000 R. P. M. At this higher speed throttle valve 5 still remainsclosed, and the mixture for combustion is supplied exclusively by theidle system of the carburetor through the secondary manifold in a mannerthe same as that above described.

Further operation of the engine controller will progressively open thethrottle valve 5. The increased flow of air through the mixture conduit3 and the venturi 4 will bring into operation the main fuel nozzle 40.At the same time, if the atmospheric bleed port 51 is located adjacentthe edge of the throttle valve 5, the flow of air will produce a drop inpressure adjacent this port 51 to enrich the mixture in the idle systemof the carburetor. This will cover the transition point between theoperation of the idle system and the main nozzle system and,furthermore, it will eliminate the effects produced by deflection of theair stream in the primary manifold due to the inclined position of thethrottle valve 5. Oftentimes it has been found that throttle valvedeflection is a serious cause of poor distribution. In this invention,however, since the primary source of fuel is from the secondary manifoldduring early stages of throttle valve opening, the effectof deflectionfrom the throttle valve will be negligible.

At some point in the operation of the engine controller to open thethrottle valve 5, the engine speed and intake air velocity will becomesufiicient to bring the nozzle 40 into full operation, but, before thishas happened, the mixture supplied through the secondary manifold hasdecreased so as to have little effect upon the mixture ratio enteringthe engine, and, although it may happen that the secondary manifoldcontinues to operate throughout the entire range of throttle positionsand engine speeds, its delivery will be so reduced in the range of wideopen throttle positions that it can be readily compensated for byadjustments of the main nozzle needle valve 35. Consequently, it makeslittle difference in this range of throttle positions whether thesecondary manifold continues to operate or not, since its effect can becompensated for in the calibration of the carburetor.

Turning now to Fig. 4, the top view of the carburetor manifoldcombination is similar to that shown in Fig. l, and the same partshavebeen indicated by the same reference characters. In thismodification, the connection of the idle system with the secondarymanifold has been modified slightly to provide a single connection 60with the secondary manifold 84 and 85. This modified form of secondarymanifold is U-shaped and provided with a mixture conduit connection inone leg of the U. In design it is, therefore, substantially identicalwith the primary manifold, which has a U-shaped passage 69 and a mixtureconduit connection 3 in one leg of the U. It has been found that thisdesign for the secondary manifold provides improved distribution, andthat the combination of a primary and a secondary manifold ofsubstantially identical shape is beneficial to engine performance forthis reason.

The modification shown in Fig. 4 is the same in other respects as theone above described in Figs. 1 and 3.

A structure has been described above which will carry out all theobjects of the present invention, but it should be understood that thisdescription is by way of illustration only, since obvious modificationswill occur to anyone skilled in the art.

I claim:

1. A charge-forming device for internal combustion engines comprising,in combination, a carburetor, including a mixture conduit, a fuel bowl,a high-speed fuel nozzle system supplied with fuel from said bowl andopening in said mixture conduit, a throttle in said mixture conduitposterior of said high-speed fuel nozzle, a low-speed fuel nozzlesystem, an idle tube for said lowspeed fuel nozzle system supplied withfuel from said high-speed nozzle system, independent means to meter thefuel supply to said low-speed fuel nozzle system, and an atmospheric airbleed for said low-speed fuel nozzle system adjacent said independentmeans to meter said fuel and controlled by throttle position, means fordistributing the mixture supplied by said carburetor, including a firstmanifold connected with said mixture conduit under control of saidthrottle, a second manifold con nected with said low-speed fuel nozzlesystem regulated by said independent fuel metering means and saidthrottle, and means for supplying a metered amount of air to said firstmanifold when said throttle is closed to the idle position.

2. The combination defined in the preceding claim including outletnozzles for said second manifold projecting into said first manifold.

References Cited in the file of this patent UNITED STATES PATENTS1,069,502 Wadsworth Aug. 5, 1913 2,621,030 Henning Dec. 9, 19522,639,699 Kiekhaefer May 26, 1953 2,656,166 Foster Oct. 20, 1953

